This invention relates to an ignition coil unit for an internal combustion engine.
FIG. 5 is a circuit diagram illustrating an ignition coil unit for an internal combustion engine which comprises an ignition coil 1 and an ignitor 2. As illustrated in FIGS. 6 and 7, the conventional ignition coil unit comprises the ignition coil 1 which is enclosed within a case 3 and attached to one side of a heat sink 5 in the form of a metal plate having a substantially L-shaped cross section by means of screws 6. The ignitor 2 is also enclosed within a case 4 and attached to the other side of the heat sink 5 by means of screws 7. The ignition coil 1 and the ignitor 2 are independent separate members, so that the ignition coil unit is large in overall dimension and needs a large installation space and, since the ignition coil unit must be assembled by screws, manufacturing cost is high and manufacturing efficiency is not satisfactory.
FIGS. 8 and 9 illustrate a front view and a side view, respectively, of another example of a conventional ignition coil unit in which the ignition coil 1 is enclosed within the coil case 3 and has a magnetic iron core 8, a high-tension tower 9 for providing a high-tension output therefrom and a connector 10 for establishing an electrical connection for activating the ignitor 2. The ignitor 2 is enclosed within the case 4 and is attached to a heat sink 11 which is attached to the iron core 8 by means of screws 12. As best illustrated in FIG. 8, the ignitor 2 is supported by the heat sink 11 which is a canti-levered member supported at only one end. Accordingly, the ignitor 2 supported by the canti-levered heat sink 11 is easily vibrated when subjected to the vibration of an engine or a vehicle, so that the ignition coil unit is not entirely satisfactory in terms of its vibration durability.